According to my instructor, water filters the "white" light from the sun in such a way that mostly blue/green is all that is left at depth. But if you carry a dive light, this is a white light source that should really show off the colors of the marine life.

And don't forget, someone is manufacturing masks with color correcting lenses. These are something that I definitely want to try.

At a recent dive club meeting, they showed off a dive light that throws the same "color" light as sunlight. Looks a bit weird in a dark room, but the results underwater were impressive. Presenter said you could also use this with your photography to get the bright colors of the coral and marine life.